Typically, methods of forming TCOs on glass substrates require high glass substrate temperatures. Such methods include chemical pyrolysis where precursors are sprayed onto the glass substrate at approximately 400 to 500 degrees C., and vacuum deposition where the glass substrate is kept at about 150 to 300 degrees C. Unfortunately, TCO films such as SnO2:F (fluorine doped tin oxide) formed on glass substrates by chemical pyrolysis suffer from non-uniformity and thus may be unpredictable and/or inconsistent with respect to certain optical and/or electrical properties.
Sputter deposition of a TCO (transparent conductive oxide) at approximately room temperature would be desirable, given that most float glass manufacturing platforms are not equipped with in-situ heating systems. An additional potential advantage of sputter-deposited TCO films is that they may include the integration of anti-reflection coatings, resistivity reduction, and so forth.
There is often a need to thermally temper coated articles having a glass substrate coated with a TCO film/coating. For instance, in certain applications tempering is required by code (e.g., e.g., for windows over doorways, for windows identified as breakable windows for firemen, and other applications). Thermal tempering typically requires heating the glass substrate with a coating thereon in a tempering furnace at a temperature of at least about 580 degrees C., more preferably at least about 600 degrees C., and often at least about 620 or 640 degrees C. (e.g., for at least about 2 minutes, more preferably for at least about 5 minutes). Thus, it will be appreciated that thermal tempering involves very high temperatures.
Unfortunately, it has been found that glass substrates supporting sputter-deposited TCOs cannot be thermally tempered without the TCOs suffering a significant loss in electrical conductivity. Glass tempering temperatures (see above) of typical sputter-deposited films causes a rapid conductivity drop in certain TCOs (e.g., sputter-deposited zinc oxide inclusive TCOs).
Thus, it will be appreciated that there exists a need in the art for an improved technique or method of tempering glass substrates including a film/coating thereon that can result in an effective and/or efficient tempered glass substrate with a TCO film thereon.
Single layer TCO coatings with large thicknesses (e.g., at least about 2,000 Å thick) formed directly on and contacting glass substrates may also be problematic in certain instances in that they may suffer from significant color non-uniformity. For instance, such a coated article may appear one color (e.g., roughly green) in transmission when looking through the coated article, but may appear reddish or pinkish in color when viewing that coated article based on reflective color at high viewing angles. As another example, such a coated article may have a fairly neutral reflective color at a zero degree (normal) viewing angle, but may appear very reddish at a 45 degree viewing angle. In other words, such coated articles with single layer TCO coatings with large thicknesses may suffer from significant angular color dependence problems.
Thus, it will be appreciated that there exists a need in the art for an improved technique or method of tempering glass substrates including a film/coating thereon that can result in an effective and/or efficient tempered glass substrate with a TCO film thereon, which does not suffer from extreme color non-uniformity.
In certain example embodiments of this invention, a method is provided for making a thermally tempered coated article including a tempered glass substrate with a TCO film thereon. Initially, color compression system including at least first and second layers is deposited by sputtering or the like, on a non-tempered glass substrate. In certain example embodiments, the first layer of the color compression system is a high index (n) layer and is deposited directly on and contacting the glass substrate, and the second layer of the color compression system is a low index (n) layer that is deposited on the glass substrate over the first layer. After the first and second layers of the color compression system have been deposited on the glass substrate, an amorphous metal oxide film is sputter-deposited onto the non-tempered glass substrate over the layers of the color compression system. In certain example embodiments, the sputter-deposited amorphous metal oxide film may be of or include an oxide of Sn and/or Sb (e.g., SnOx:Sb). As sputter-deposited, the amorphous metal oxide film is rather high with respect to visible light absorption, has a high sheet resistance (i.e., not truly conductive), and is amorphous.
Then, the glass substrate with the amorphous film and the color compression system thereon is thermally tempered. The thermal tempering typically involves heating the glass substrate with the amorphous film and the color compression system thereon in a tempering furnace at a temperature of at least about 580 degrees C., more preferably at least about 600 degrees C., and often at least about 620 or 640 degrees C. The glass substrate with the layers thereon may be in the tempering furnace for at least about 2 minutes, more preferably for at least about 5 minutes, in certain example embodiments of this invention. The thermal tempering causes at least the amorphous non-conductive film to be transformed into a crystalline transparent conductive oxide (TCO) film. In other words, the heat used in the thermal tempering of the glass substrate causes the amorphous film to turn into a crystalline film, causes the visible transmission of the film to increase, and causes the film to become electrically conductive. In short, the thermal tempering activates at least the top layer of the layer stack.
The color compression system, including the first and second layers thereof, provided between the glass substrate and the TCO film reduces color non-uniformity characteristics of the coated article compared to if the color compression system were not present. For example, in certain example embodiments of this invention, the color compression system permits the coated article to realize a more uniform and more consistent color at both normal and off-axis viewing angles, even in the situation where a rather thick (e.g., from about 1,000 to 10,000 Å thick, more preferably from about 2,000 to 10,000 Å thick, and most preferably from about 3,000 to 8,000 Å thick) TCO is the top layer of the layer stack. In general, a more neutral colored coated article can be provided.
In certain example embodiments of this invention, the amorphous film prior to tempering and the crystalline TCO (e.g., the top layer of the layer stack) following tempering may be of or include SnOx:Sb (x may be from about 0.5 to 2, more preferably from about 1 to 2, and sometimes from about 1 to 1.95). The film may be oxygen deficient (substoichiometric in certain instances). The Sn and Sb may be co-sputtered in an oxygen inclusive atmosphere (e.g., a mixture of oxygen and argon) to form the film in certain example embodiments of this invention, with the Sb being provided to increase conductivity of the crystalline film following tempering. In certain example embodiments, the Sb is provided for doping purposes, and can make up from about 0.001 to 30% (weight %) of the amorphous and/or crystalline metal oxide film (from preferably from about 1 to 15%, with an example being about 8%). If the Sb content is higher than this, the lattice is disturbed too much and mobility of electrons is also disturbed thereby hurting conductivity of the film, whereas if less than this amount of Sb is provided then the conductivity is not as good in the crystalline film.
In certain example embodiments of this invention, there is provided a method of making a thermally tempered coated article including a transparent conductive film on a tempered glass substrate, the method comprising: providing a glass substrate; sputter-depositing a high index layer having a high refractive index on the glass substrate, and then sputter-depositing a low index layer having a low refractive index on the glass substrate over at least the high index layer; after the high index layer and the low index layer have been sputter-deposited on the glass substrate, sputter-depositing an amorphous film on the glass substrate over each of the high index layer and the low index layer; thermally tempering the glass substrate with the amorphous film, the low index layer, and the high index layer thereon; and wherein heat used in said tempering causes at least the amorphous film to transform into a crystalline film, and wherein the crystalline film is transparent to visible light and electrically conductive following said tempering. The color compression system may be made up of at least the high and low index layers.
In other example embodiments of this invention, there is provided a method of making a thermally tempered coated article including a transparent conductive film on a tempered glass substrate, the method comprising: providing a glass substrate; forming a high index layer having a high refractive index on the glass substrate, and a low index layer having a low refractive index on the glass substrate over at least the high index layer; after the high index layer and the low index layer have been formed, forming an amorphous film comprising a metal oxide on the glass substrate over each of the high index layer and the low index layer; thermally tempering the glass substrate with the amorphous film, the low index layer, and the high index layer thereon; and wherein heat used in said tempering causes at least the amorphous film to transform into a film which is substantially transparent and electrically conductive.
In still further example embodiments of this invention, there is provided a coated article comprising: a thermally tempered glass substrate; a high index layer having a high refractive index provided on the glass substrate, and a low index layer having a low refractive index provided on the glass substrate over at least the high index layer; and a crystalline transparent conductive film comprising a metal oxide supported by at least the tempered glass substrate and provided over at least the high index layer and the low index layer, wherein the crystalline transparent conductive film comprises an oxide of Sn and Sb.
In certain example embodiments of this invention, there is provided a method of making a thermally tempered coated article including a transparent conductive film on, directly or indirectly, a tempered glass substrate, the method comprising: providing a glass substrate; sputter-depositing an amorphous film comprising Sn and Sb on the glass substrate (directly or indirectly); thermally tempering the glass substrate with the amorphous film comprising Sn and Sb thereon; and wherein heat used in said tempering causes the amorphous film to transform into a crystalline film, and wherein the crystalline film is transparent to visible light and electrically conductive.